The original idea behind `std.sparc' was that the std.$MACHINE file
would have those things that were absolutely required for that kind
of machine (e.g., you might have a std.780 and std.750 for VAXen to
declare the main bus and memory controllers, and define the right cpu
type macro). So std.sparc should have only those things that are
absolutely for-sure on a sparc.
Note that include files can include other files, so you can have
a std.sun4c that includes other stuff, or `std.headless', etc.
Chris